Chapter 2. CP/MAS Solids Operation
19
VNMR 6.1C User Guide: Solid-State NMR
01-999162-00 C0402
UNITY Systems
Fine attenuator control is provided over a 6 db range in steps from 0 of 4095 on one or both
transmitter boards. It is necessary to use both the fine and course attenuators on UNITY
systems to set the power levels for CP/MAS experiments. UNITY systems use the same
XPOLAR1 aliases described above. In addition a new coarse power setting,
cppwr
(alias
for
dpwr
) used during cross polarization, is crated by setting
dblvl2=’y’
. The
parameter
dpwr
then applies only to the decoupling power. UNITY systems with a fine
attenuator only on the highband channel must first set the observe power using the course
attenuator and then high band channel using both the course and fine attenuators. CP/MAS
is very difficult if the fine attenuators are absent on both channels.
The XPOLAR sequence (described in older versions of this manual) can be used with
UNITY systems.
Pneumatics and Tachometer Box and Rotor Speed Control
A pneumatics/tachometer box is used for controlling air flow and spinning speeds of MAS
rotors for all systems. A manual box allows adjustment of bearing and drive pressure with
knobs and is independent of the console. Alternatively a rotor speed controller is available
for
UNITY
INOVA and all MERCURY systems with the solid option. Rotor speed control is
obtained by modulation of the drive flow and is under computer control. The Rotor Speed
Controller tachometer box is distinguished from the manual tachometer box by a 9 pin
connector on the lower right. The connector is used to connect the optional cable from the
tachometer box to the back of the acquisition computer on
UNITY
INOVA or the to Spinner
board in the magnet leg on MERCURY systems. Rotor speed control software is located in
the MSR board of INOVA and the Spinner board of MERCURY systems. A
UNITY
INOVA
system equipped with both the Rotor Synchronization and Rotor Speed Control options and
appropriate cables for the acquisition computer can trigger pulses on the tachometer signal
using the pulse sequence commands
xgate
,
rorotsync
, and
rotorperiod
.
The operation of the Pneumatics and Tachometer Box is described in section
.
An older standalone PC may be present to provide rotor speed control for UNITYplus and
UNITY. Instructions for this controller are provided in older manuals.